CHARATER OF SEISMICITY BEFORE THE M_S≥5.5 EARTHQUAKES IN HETAO BASIN

The earthquake data (M_L≥2.0)from 1970 to Aug.2000 in Hetao and its adjacent area (38.5°~40°N,106°~113°E)are processed with the method achieved in the scientific breakthrough project during "Eighth five years plan" and "Ninth five years plan" period.Through a thorough scan and analysis to the seismicity and seismometry index for the medium and strong earthquakes in the region,we pick up some seismicity images and parameters that have the function of prediction.Using these images and parameters we analyzed the geological tectonic feature,the earthquakes' distribution character and the recent seismicities in the area.We believe the seismic risk can not be ignored in hetao region.